Refrigeration cycle apparatus

ABSTRACT

A refrigeration cycle apparatus includes a compressor, an expansion valve, a flow switching device, a heat source side heat exchanger including a first heat source side heat exchanger and a second heat source side heat exchanger connected in parallel, an opening-and-closing valve provided on downstream of the second heat source side heat exchanger through which refrigerant flows during a defrosting operation, and a controller that, when the defrosting operation is performed, controls the flow switching device so that the refrigerant discharged from the compressor flows into the heat source side heat exchanger. The controller switches the opening-and-closing valve from an open state to a closed state when the defrosting operation is started, determines a point in time when defrosting targets to be defrosted are switched, and switches the opening-and-closing valve from the closed state to the open state in accordance with the point in time determined.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. National Stage Application of InternationalApplication No. PCT/JP2019/044375 filed on Nov. 12, 2019, the contentsof which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a refrigeration cycle apparatus thatconditions air in an air-conditioned space.

BACKGROUND

In an existing air-conditioning apparatus, there is a heat exchangerincluding a plurality of flat pipes that are vertically arrayed and eachhave a refrigerant passage, and a plurality of fins that partition aspace between adjacent flat pipes into a plurality of air flow passagesthrough which air flows (for example, see Patent Literature 1).

A heat exchanger disclosed in Patent Literature 1 includes a main heatexchange section, and a sub heat exchange section provided at a positiondifferent from a position of the main heat exchange section in avertical direction and connected in series with the main heat exchangesection. In the main heat exchange section, many flat pipes are providedin comparison with the sub heat exchange section located downstream ofthe main heat exchange section. Furthermore, a lowermost flat pipe inthe heat exchanger is provided in a main heat exchanger located upstreamof the sub heat exchange section. This configuration reduces the timetaken to melt frost that has adhered to a lowermost heat exchangesection during a defrosting operation.

PATENT LITERATURE

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2019-11941

In an air conditioner disclosed in Patent Literature 1, in thedefrosting operation, refrigerant discharged from a compressor passesthrough the main heat exchange section and then flows into the sub heatexchange section. That is, even after defrosting of the main heatexchange section is finished, the refrigerant discharged from thecompressor flows through the main heat exchange section before flowinginto the sub heat exchange section. For this reason, before the heat ofthe refrigerant reaches the sub heat exchange section, heat exchangebetween the refrigerant and air is performed in the main heat exchangesection in which defrosting is unnecessary, and the heat is uselesslyreleased. Consequently, defrosting is unable to be efficientlyperformed.

SUMMARY

The present disclosure has been made to overcome such an issue andprovides a refrigeration cycle apparatus capable of efficientlyperforming defrosting.

A refrigeration cycle apparatus according to an embodiment of thepresent disclosure includes a compressor configured to compress anddischarge refrigerant; an expansion valve configured to reduce pressureof the refrigerant to cause the refrigerant to expand; a load side heatexchanger connected to the expansion valve; a flow switching deviceconnected to the compressor and the load-side heat exchanger; a heatsource side heat exchanger including a first heat source side heatexchanger and a second heat source side heat exchanger connected inparallel between the flow switching device and the expansion valve; anopening-and-closing valve provided on downstream of the second heatsource side heat exchanger through which the refrigerant flows during adefrosting operation; and a controller configured to, when thedefrosting operation is performed, control the flow switching device sothat the refrigerant discharged from the compressor flows into the heatsource side heat exchanger. The controller includes a first defrostingunit configured to switch the opening-and-closing valve from an openstate to a closed state when the defrosting operation is started, adetermination unit configured to determine a point in time whendefrosting targets to be defrosted are switched, and a second defrostingunit configured to switch the opening-and-closing valve from the closedstate to the open state in accordance with the point in time determinedby the determination unit.

In the embodiment of the present disclosure, the first defrosting unitcloses the opening-and-closing valve when defrosting is started, andthus the refrigerant discharged from the compressor flows intensively tothe first heat source side heat exchanger of two heat source side heatexchangers. Subsequently, when the second defrosting unit opens theopening-and-closing valve, most of the heat of the refrigerant isconsumed to defrost the second heat source side heat exchanger. Thus,the heat of the refrigerant is kept from being uselessly consumed incomparison with a case where two heat source side heat exchangersconnected in series are simultaneously defrosted. Consequently, the twoheat source side heat exchangers can be efficiently defrosted.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a refrigerant circuit diagram illustrating an exampleconfiguration of a refrigeration cycle apparatus according to Embodiment1.

FIG. 2 is a functional block diagram illustrating an exampleconfiguration of a controller illustrated in FIG. 1.

FIG. 3 is a hardware configuration diagram illustrating an exampleconfiguration of the controller illustrated in FIG. 2.

FIG. 4 is a hardware configuration diagram illustrating another exampleconfiguration of the controller illustrated in FIG. 2.

FIG. 5 is a flowchart illustrating an example of an operation procedureperformed by the refrigeration cycle apparatus illustrated in FIG. 1.

FIG. 6 is a refrigerant circuit diagram illustrating an exampleconfiguration of a refrigeration cycle apparatus in Modification 1.

FIG. 7 is a functional block diagram illustrating an exampleconfiguration of the controller in Modification 1.

FIG. 8 is a refrigerant circuit diagram illustrating an exampleconfiguration of a refrigeration cycle apparatus in Modification 2.

FIG. 9 is a functional block diagram illustrating an exampleconfiguration of the controller in Modification 2.

FIG. 10 is a flowchart illustrating an example of an operation procedureperformed by the refrigeration cycle apparatus illustrated in FIG. 8.

FIG. 11 is a refrigerant circuit diagram illustrating an exampleconfiguration of a refrigeration cycle apparatus in Modification 3.

FIG. 12 is a refrigerant circuit diagram illustrating an exampleconfiguration of a refrigeration cycle apparatus according to Embodiment2.

FIG. 13 is a side view illustrating an example configuration of a firstheat source side heat exchanger illustrated in FIG. 12.

FIG. 14 is a side view illustrating an example configuration of a secondheat source side heat exchanger illustrated in FIG. 12.

FIG. 15 is a refrigerant circuit diagram illustrating an exampleconfiguration of a refrigeration cycle apparatus in a comparativeexample.

FIG. 16 is a flowchart illustrating an example of an operation procedureperformed by the refrigeration cycle apparatus in the comparativeexample illustrated in FIG. 15.

FIG. 17 includes graphs illustrating an example of the relationshipbetween a refrigerant flow rate and a position of a heat source sideheat exchanger during a defrosting operation.

FIG. 18 is a refrigerant circuit diagram illustrating an exampleconfiguration of a refrigeration cycle apparatus according to Embodiment3.

FIG. 19 is an external perspective view illustrating an exampleconfiguration of a heat source side unit illustrated in FIG. 18.

FIG. 20 is an external perspective view of the heat source side unitillustrated in FIG. 18 as seen from a direction different from that inFIG. 19.

FIG. 21 is a schematic view illustrating the layout of heat source sideheat exchangers in the heat source side unit illustrated in FIG. 20 asseen from above.

FIG. 22 is a side view illustrating an example configuration of a firstdivision heat exchanger illustrated in FIG. 19.

FIG. 23 is a side view illustrating an example configuration of thesecond heat source side heat exchanger illustrated in FIG. 20.

FIG. 24 is a refrigerant circuit diagram illustrating an exampleconfiguration of a refrigeration cycle apparatus in Modification 4.

DETAILED DESCRIPTION Embodiment 1

A configuration of a refrigeration cycle apparatus in Embodiment 1 willbe described. FIG. 1 is a refrigerant circuit diagram illustrating anexample configuration of the refrigeration cycle apparatus according toEmbodiment 1. As illustrated in FIG. 1, a refrigeration cycle apparatus1 includes a heat source side unit 10, load side units 20 a and 20 b,and a controller 30 that controls refrigerant devices included in theheat source side unit 10 and the load side units 20 a and 20 b. AlthoughFIG. 1 illustrates the case where the refrigeration cycle apparatus 1includes two load side units that are the load side units 20 a and 20 b,the number of load side units may be one or may be three or more.

The heat source side unit 10 includes a compressor 2 that compresses anddischarges refrigerant, a heat source side heat exchanger 15 that causesthe refrigerant to exchange heat with outside air, a flow switchingdevice 5, an accumulator 6, and an opening-and-closing valve 7. The heatsource side heat exchanger 15 includes a first heat source side heatexchanger 3 and a second heat source side heat exchanger 4. The loadside unit 20 a includes a load side heat exchanger 21 a that causes therefrigerant to exchange heat with air in a room where the load side unit20 a is installed, and an expansion valve 22 a that reduces the pressureof the refrigerant to cause the refrigerant to expand. The load sideunit 20 b includes a load side heat exchanger 21 b that causes therefrigerant to exchange heat with air in a room where the load side unit20 b is installed, and an expansion valve 22 b that reduces the pressureof the refrigerant to cause the refrigerant to expand.

The first heat source side heat exchanger 3 and the second heat sourceside heat exchanger 4 are connected in parallel between the flowswitching device 5 and the expansion valves 22 a and 22 b. Of tworefrigerant inlet/outlet ports of the first heat source side heatexchanger 3, one refrigerant inlet/outlet port is connected to a firstgas pipe 43 a, and the other refrigerant inlet/outlet port is connectedto a first liquid pipe 44 a. Of two refrigerant inlet/outlet ports ofthe second heat source side heat exchanger 4, one refrigerantinlet/outlet port is connected to a second gas pipe 43 b, and the otherrefrigerant inlet/outlet port is connected to a second liquid pipe 44 b.The first gas pipe 43 a and the second gas pipe 43 b are joined to a gaspipe 41 and communicate with the flow switching device 5. The firstliquid pipe 44 a and the second liquid pipe 44 b are joined to a liquidpipe 47 and communicate with the expansion valves 22 a and 22 b. Theopening-and-closing valve 7 is provided in the second liquid pipe 44 b.

The flow switching device 5 is connected to the load side heatexchangers 21 a and 21 b via a refrigerant pipe 42 and is connected tothe accumulator 6 via a refrigerant pipe 48. Furthermore, the flowswitching device 5 is connected to the compressor 2 and the accumulator6 via a refrigerant pipe 49. The accumulator 6 is connected to arefrigerant inlet of the compressor 2. The compressor 2, the first heatsource side heat exchanger 3 and the second heat source side heatexchanger 4, the expansion valve 22 a, and the load side heat exchanger21 a are connected with pipes, such as the refrigerant pipe 42, to forma refrigerant circuit 60 a. Furthermore, the compressor 2, the firstheat source side heat exchanger 3 and the second heat source side heatexchanger 4, the expansion valve 22 b, and the load side heat exchanger21 b are connected with pipes, such as the refrigerant pipe 42, to forma refrigerant circuit 60 b.

In the second heat source side heat exchanger 4, a heat exchangertemperature sensor 11 is provided that detects a temperature Te ofrefrigerant. In the second liquid pipe 44 b, a refrigerant temperaturesensor 12 is provided that detects a temperature Tn2 of refrigerant thatflows through the second liquid pipe 44 b. In the load side unit 20 a, aroom temperature sensor 23 a is provided that detects a temperature ofair in the room where the load side unit 20 a is installed. In the loadside unit 20 b, a room temperature sensor 23 b is provided that detectsa temperature of air in the room where the load side unit 20 b isinstalled. The heat exchanger temperature sensor 11, the refrigeranttemperature sensor 12, and the room temperature sensors 23 a and 23 bare, for example, thermistors. The heat exchanger temperature sensor 11may be provided on a first heat source side heat exchanger 3 side inplace of the second heat source side heat exchanger 4.

The compressor 2 is a compressor whose displacement is variable, forexample, an inverter compressor. The accumulator 6 is a container thatkeeps liquid refrigerant from being sucked into the compressor 2. Theexpansion valves 22 a and 22 b are, for example, electronic expansionvalves. The flow switching device 5 switches, to the gas pipe 41 or therefrigerant pipe 42, a direction in which the refrigerant dischargedfrom the compressor 2 flows. The flow switching device 5 is, forexample, a four-way valve. The opening-and-closing valve 7 is, forexample, a shutoff valve whose state can be switched, of a closed stateand an open state, from one state to the other state. Theopening-and-closing valve 7 may be an electronic expansion valve thatadjusts a flow rate of refrigerant that circulates. The first heatsource side heat exchanger 3 and the second heat source side heatexchanger 4, and the load side heat exchangers 21 a and 21 b are, forexample, fin-and-tube heat exchangers.

The controller 30 is connected to, via a signal line not illustrated inthe figure, devices that are the compressor 2, the flow switching device5, the expansion valves 22 a and 22 b, and the opening-and-closing valve7. Furthermore, the controller 30 is connected to, via a signal line notillustrated in the figure, sensors that are the room temperature sensors23 a and 23 b, the heat exchanger temperature sensor 11, and therefrigerant temperature sensor 12. Communication connections of thecontroller 30 to the devices that are the compressor 2, the flowswitching device 5, the expansion valve 22 a, the expansion valve 22 b,and the opening-and-closing valve 7 may be established not only by wirebut also wirelessly. Regarding the sensors as well, communicationconnections of the controller 30 to the sensors that are the roomtemperature sensor 23 a, the room temperature sensor 23 b, the heatexchanger temperature sensor 11, and the refrigerant temperature sensor12 may be established not only by wire but also wirelessly.

Before a configuration of the controller 30 illustrated in FIG. 1 willbe described, the flow of refrigerant in each of operation modes of therefrigeration cycle apparatus 1 will be simply described. Here, the caseof the refrigerant circuit 60 a will be described. Furthermore, assumethat the opening-and-closing valve 7 is in an open state.

[Cooling Operation]

First, the flow of refrigerant in the case where the refrigeration cycleapparatus 1 performs a cooling operation will be described withreference to FIG. 1. In the case where the refrigeration cycle apparatus1 performs the cooling operation, the controller 30 switches betweenflow passages of the flow switching device 5 so that refrigerantdischarged from the compressor 2 flows into the first heat source sideheat exchanger 3 and the second heat source side heat exchanger 4. Whenlow-temperature, low-pressure refrigerant is compressed by thecompressor 2, high-temperature, high-pressure gaseous refrigerant isdischarged from the compressor 2. The gaseous refrigerant dischargedfrom the compressor 2 flows through the flow switching device 5 andflows into the first heat source side heat exchanger 3 and the secondheat source side heat exchanger 4. The refrigerant having flowed intothe first heat source side heat exchanger 3 and the second heat sourceside heat exchanger 4 is condensed into low-temperature, high-pressureliquid refrigerant by exchanging heat with air in these heat exchangersconnected in parallel and flows out of the first heat source side heatexchanger 3 and the second heat source side heat exchanger 4.

The liquid refrigerant having flowed out of the first heat source sideheat exchanger 3 and the second heat source side heat exchanger 4 iscaused to turn into low-temperature, low-pressure liquid refrigerant bythe expansion valve 22 a. The liquid refrigerant flows into the loadside heat exchanger 21 a. The refrigerant having flowed into the loadside heat exchanger 21 a evaporates into low-temperature, low-pressuregaseous refrigerant by exchanging heat with air in the load side heatexchanger 21 a and flows out of the load side heat exchanger 21 a. Inthe load side heat exchanger 21 a, when the refrigerant receives heatfrom air in the room, the air in the room is cooled. The refrigeranthaving flowed out of the load side heat exchanger 21 a is sucked intothe compressor 2 via the flow switching device 5. During the coolingoperation, a cycle is repeated in which the refrigerant discharged fromthe compressor 2 flows through the first heat source side heat exchanger3 and the second heat source side heat exchanger 4, the expansion valve22 a, and the load side heat exchanger 21 a in sequence and then issucked into the compressor 2.

[Heating Operation]

Next, the flow of refrigerant in the case where the refrigeration cycleapparatus 1 performs a heating operation will be described withreference to FIG. 1. In the case where the refrigeration cycle apparatus1 performs the heating operation, the controller 30 switches between theflow passages of the flow switching device 5 so that refrigerantdischarged from the compressor 2 flows into the load side heat exchanger21 a. When low-temperature, low-pressure refrigerant is compressed bythe compressor 2, high-temperature, high-pressure gaseous refrigerant isdischarged from the compressor 2. The high-temperature, high-pressuregaseous refrigerant discharged from the compressor 2 flows through theflow switching device 5 and flows into the load side heat exchanger 21a. The refrigerant having flowed into the load side heat exchanger 21 ais condensed into high-temperature, high-pressure liquid refrigerant byexchanging heat with air in the load side heat exchanger 21 a and flowsout of the load side heat exchanger 21 a. In the load side heatexchanger 21 a, when the refrigerant transfers heat to air in the room,the air in the room is heated.

The high-temperature, high-pressure liquid refrigerant having flowed outof the load side heat exchanger 21 a is caused to turn intolow-temperature, low-pressure liquid refrigerant by the expansion valve22 a. The liquid refrigerant flows into the first heat source side heatexchanger 3 and the second heat source side heat exchanger 4. In thefirst heat source side heat exchanger 3 and the second heat source sideheat exchanger 4, the refrigerant evaporates into low-temperature,low-pressure gaseous refrigerant by exchanging heat with air and flowsout of the first heat source side heat exchanger 3 and the second heatsource side heat exchanger 4. The refrigerant having flowed out of thefirst heat source side heat exchanger 3 and the second heat source sideheat exchanger 4 is sucked into the compressor 2 via the flow switchingdevice 5. While the refrigeration cycle apparatus 1 is performing theheating operation, a cycle is repeated in which the refrigerantdischarged from the compressor 2 flows through the load side heatexchanger 21 a, the expansion valve 22 a, and the first heat source sideheat exchanger 3 and the second heat source side heat exchanger 4 insequence and then is sucked into the compressor 2.

[Defrosting Operation]

The flow of refrigerant in the case where the refrigeration cycleapparatus 1 performs a defrosting operation will be described withreference to FIG. 1. In the case where the refrigeration cycle apparatus1 switches an operation mode from the heating operation to thedefrosting operation, the controller 30 switches between the flowpassages of the flow switching device 5 so that refrigerant dischargedfrom the compressor 2 flows into the first heat source side heatexchanger 3 and the second heat source side heat exchanger 4.Furthermore, the controller 30 performs control to put the expansionvalve 22 a in a fully open state. In the case of the defrostingoperation, a direction in which refrigerant in the refrigerant circuit60 a flows is the same as that in the cooling operation, and thus adetailed description of the flow of the refrigerant is omitted.

Next, a configuration of the controller 30 illustrated in FIG. 1 will bedescribed. FIG. 2 is a functional block diagram illustrating an exampleconfiguration of the controller illustrated in FIG. 1.

The controller 30 includes a refrigeration cycle control unit 51, adetermination unit 52, a timer 53, a first defrosting unit 54, and asecond defrosting unit 55. Regarding the controller 30, variousfunctions are implemented by an arithmetic unit, such as amicrocomputer, executing software. Furthermore, the controller 30 may beconstituted by hardware, such as a circuit device, that implementsvarious functions. A set temperature Ts1 is input to the controller 30via a remote controller not illustrated in the figure by a user thatuses the load side unit 20 a. A set temperature Ts2 is input to thecontroller 30 via a remote controller not illustrated in the figure by auser that uses the load side unit 20 b. Incidentally, in therefrigeration cycle apparatus 1 illustrated in FIG. 1, a location wherethe controller 30 is installed is not limited to the illustratedlocation, and the controller 30 may be provided in the heat source sideunit 10, or may be provided in the load side unit 20 a or 20 b.

The refrigeration cycle control unit 51 controls the flow switchingdevice 5 in accordance with an operation mode of the refrigeration cycleapparatus 1. The refrigeration cycle control unit 51 controls anoperating frequency of the compressor 2 and opening degrees of theexpansion valves 22 a and 22 b by using detected values received fromthe room temperature sensors 23 a and 23 b and the set temperatures Ts1and Ts2. Specifically, the refrigeration cycle control unit 51 controlsthe operating frequency of the compressor 2 and the opening degrees ofthe expansion valves 22 a and 22 b so that the detected value of theroom temperature sensor 23 a approaches the set temperature Ts1 and thedetected value of the room temperature sensor 23 b approaches the settemperature Ts2.

While the refrigeration cycle apparatus 1 is performing the heatingoperation, the refrigeration cycle control unit 51 monitors thetemperature Te of refrigerant received from the heat exchangertemperature sensor 11 and determines whether or not the temperature Teof refrigerant is not more than a predetermined temperature thresholdT0. The temperature threshold T0 is, for example, 0 degrees C. When thetemperature Te of refrigerant reaches not more than the temperaturethreshold T0, the refrigeration cycle control unit 51 controls the flowswitching device 5 to switch between the flow passages and alsotransmits, to the determination unit 52, defrosting start informationrepresenting that the defrosting operation has been started. When therefrigeration cycle control unit 51 receives defrosting completioninformation from the determination unit 52, the refrigeration cyclecontrol unit 51 controls the flow switching device 5 to switch betweenthe flow passages and switches the operation mode from the defrostingoperation to the heating operation.

The timer 53 measures a time period and provides measurement timeinformation to the determination unit 52. The determination unit 52determines, in accordance with at least either a time period that haselapsed since the start of defrosting or the temperature Tn2 ofrefrigerant detected by the refrigerant temperature sensor 12, a pointin time when defrosting targets to be defrosted are switched. When thedetermination unit 52 receives the defrosting start information from therefrigeration cycle control unit 51, the determination unit 52 transfersthe defrosting start information to the first defrosting unit 54 andalso monitors a time t1 representing a time period that has elapsedsince the start of defrosting. The determination unit 52 determineswhether or not the time t1 is not less than a predetermined timethreshold tth1. The time threshold tth1 is set to a time beforedefrosting of the first heat source side heat exchanger 3 is completelyfinished. When the time t1 reaches not less than the time thresholdtth1, the determination unit 52 transmits, to the second defrosting unit55, switching instruction information representing an instruction forswitching between states of the opening-and-closing valve 7.

Furthermore, after the determination unit 52 transmits the switchinginstruction information to the second defrosting unit 55, thedetermination unit 52 monitors the temperature Tn2 of refrigerantreceived from the refrigerant temperature sensor 12 and determineswhether or not the temperature Tn2 of refrigerant is not less than apredetermined temperature threshold Tb. The temperature threshold Tb is,for example, 7 degrees C. When the temperature Tn2 of refrigerantreaches not less than the temperature threshold Tb, the determinationunit 52 transmits, to the refrigeration cycle control unit 51,defrosting completion information representing that defrosting has beencompleted.

When the first defrosting unit 54 receives the defrosting startinformation from the determination unit 52, the first defrosting unit 54switches the opening-and-closing valve 7 from an open state to a closedstate. When the second defrosting unit 55 receives the switchinginstruction information from the determination unit 52, the seconddefrosting unit 55 switches the opening-and-closing valve 7 from theclosed state to the open state.

Here, an example of hardware of the controller 30 illustrated in FIG. 2will be described. FIG. 3 is a hardware configuration diagramillustrating an example configuration of the controller illustrated inFIG. 2. In the case where various functions of the controller 30 areexecuted by hardware, the controller 30 illustrated in FIG. 2 isconstituted by a processing circuit 31 as illustrated in FIG. 3.Functions of the refrigeration cycle control unit 51, the determinationunit 52, the timer 53, the first defrosting unit 54, and the seconddefrosting unit 55 that are illustrated in FIG. 2 are implemented by theprocessing circuit 31.

In the case where each function is executed by hardware, the processingcircuit 31 corresponds, for example, to a single circuit, a complexcircuit, a programmed processor, a parallel programmed processor, anApplication Specific Integrated Circuit (ASIC), a Field-ProgrammableGate Array (FPGA), or a combination of these. Functions of units thatare the refrigeration cycle control unit 51, the determination unit 52,the timer 53, the first defrosting unit 54, and the second defrostingunit 55 may be implemented by respective processing circuits 31, or thefunctions of the units may be implemented by one processing circuit 31.

Furthermore, an example of other hardware of the controller 30illustrated in FIG. 2 will be described. FIG. 4 is a hardwareconfiguration diagram illustrating another example configuration of thecontroller illustrated in FIG. 2. In the case where various functions ofthe controller 30 are executed by software, the controller 30illustrated in FIG. 2 is constituted by a processor 71 and a memory 72as illustrated in FIG. 4. Functions of the refrigeration cycle controlunit 51, the determination unit 52, the timer 53, the first defrostingunit 54, and the second defrosting unit 55 are implemented by theprocessor 71 and the memory 72. FIG. 4 illustrates that the processor 71and the memory 72 are connected to each other in such a manner that theycan communicate with each other.

In the case where each function is executed by software, the functionsof the refrigeration cycle control unit 51, the determination unit 52,the timer 53, the first defrosting unit 54, and the second defrostingunit 55 are implemented by software, firmware, or a combination ofsoftware and firmware. Software and firmware are written as programs andstored in the memory 72. The processor 71 reads out a program stored inthe memory 72 and executes the program to thereby implement a functionof each unit.

As the memory 72, for example, non-volatile semiconductor memories, suchas a Read Only Memory (ROM), a flash memory, an Erasable andProgrammable ROM (EPROM), and an Electrically Erasable and ProgrammableROM (EEPROM), are used. Furthermore, as the memory 72, a volatilesemiconductor memory, such as a Random Access Memory (RAM), may be used.Additionally, as the memory 72, detachable recording media, such as amagnetic disk, a flexible disk, an optical disc, a Compact Disc (CD), aMini Disc (MD), and a Digital Versatile Disc (DVD), may be used.

Next, the operation of the refrigeration cycle apparatus 1 in Embodiment1 will be described. FIG. 5 is a flowchart illustrating an example of anoperation procedure performed by the refrigeration cycle apparatusillustrated in FIG. 1. FIG. 5 illustrates an example of an operationprocedure in the case where the refrigeration cycle apparatus 1 performsthe defrosting operation. Assume that the refrigeration cycle apparatus1 is performing the heating operation before starting the operationprocedure illustrated in FIG. 5 and the opening-and-closing valve 7 isin an open state.

The refrigeration cycle control unit 51 determines whether or not thetemperature Te of refrigerant received from the heat exchangertemperature sensor 11 has reached not more than the temperaturethreshold T0 (step S101). When the temperature Te of refrigerant reachesnot more than the temperature threshold T0 in step S101, therefrigeration cycle control unit 51 determines that frost has adhered tothe heat source side heat exchanger 15 and controls the flow switchingdevice 5 to switch between the flow passages (step S102). Thus, therefrigerant discharged from the compressor 2 flows through the flowswitching device 5 and flows into the heat source side heat exchanger15. Furthermore, the refrigeration cycle control unit 51 transmitsdefrosting start information to the determination unit 52 in step S102.

When the determination unit 52 receives the defrosting start informationfrom the refrigeration cycle control unit 51, the determination unit 52transfers the defrosting start information to the first defrosting unit54 and also monitors the time t1 measured by the timer 53. When thefirst defrosting unit 54 receives the defrosting start information fromthe determination unit 52, the first defrosting unit 54 closes theopening-and-closing valve 7 (step S103). The determination unit 52determines whether or not the time t1 has reached not less than the timethreshold tth1 (step S104). When the time t1 reaches not less than thetime threshold tth1 in step S104, the determination unit 52 transmitsswitching instruction information to the second defrosting unit 55.

When the second defrosting unit 55 receives the switching instructioninformation from the determination unit 52, the second defrosting unit55 opens the opening-and-closing valve 7 (step S105). After thedetermination unit 52 transmits the switching instruction information tothe second defrosting unit 55, the determination unit 52 determineswhether or not the temperature Tn2 of refrigerant received from therefrigerant temperature sensor 12 has reached not less than thetemperature threshold Tb (step S106). When the temperature Tn2 ofrefrigerant reaches not less than the temperature threshold Tb, thedetermination unit 52 determines that defrosting of the heat source sideheat exchanger 15 has been completed and transmits defrosting completioninformation to the refrigeration cycle control unit 51.

When the refrigeration cycle control unit 51 receives the defrostingcompletion information from the determination unit 52, the refrigerationcycle control unit 51 controls the flow switching device 5 to switchbetween the flow passages (step S107). Thus, the refrigerant dischargedfrom the compressor 2 flows through the flow switching device 5 andflows into the load side units 20 a and 20 b. The operation mode of therefrigeration cycle apparatus 1 returns from the defrosting operation tothe heating operation.

Thus, the first heat source side heat exchanger 3 is intensivelydefrosted from the time when the refrigeration cycle apparatus 1 startsdefrosting until the time when the time t1 reaches the time thresholdtth1. Then, the refrigeration cycle apparatus 1 starts to defrost thesecond heat source side heat exchanger 4 before defrosting of the firstheat source side heat exchanger 3 is completed, and the flow ofrefrigerant to the first heat source side heat exchanger 3 is continued.Subsequently, the determination unit 52 determines, in accordance with atemperature Tn2 of refrigerant downstream of the second heat source sideheat exchanger 4, whether or not defrosting of the second heat sourceside heat exchanger 4 has been completed. When it is determined, inaccordance with the temperature of refrigerant downstream of the secondheat source side heat exchanger 4, that defrosting of the second heatsource side heat exchanger has been completed, defrosting of the firstheat source side heat exchanger 3 has been also completed.

Incidentally, in the example configuration illustrated in FIG. 1,although the refrigerant temperature sensor 12 is provided in the secondliquid pipe 44 b, the refrigerant temperature sensor 12 may be providedin the liquid pipe 47 near the confluence of the first liquid pipe 44 aand the second liquid pipe 44 b. In this case, in step S104 illustratedin FIG. 5, the determination unit 52 determines whether or not thetemperature Tn2 of refrigerant is not less than a predeterminedtemperature threshold Ta. As a result of a determination made in stepS104, when the temperature Tn2 of refrigerant is not less than thetemperature threshold Ta, the determination unit 52 only has to transmitthe switching instruction information to the second defrosting unit 55.The relationship between the temperature thresholds Ta and Tb is, forexample, Ta>Tb. Even when the refrigeration cycle apparatus 1 proceedsto the operation of step S105 owing to the relationship of Ta>Tb beforedefrosting of the first heat source side heat exchanger 3 is completelyfinished, the refrigerant also flows through the first heat source sideheat exchanger 3, and thus the defrosting is performed. Furthermore,when the refrigerant temperature sensor 12 is provided in the liquidpipe 47, the timer 53 does not have to be provided in the controller 30.

The refrigeration cycle apparatus 1 in Embodiment 1 includes thecompressor 2, the expansion valve 22 a, the load side heat exchanger 21a, the flow switching device 5, the heat source side heat exchanger 15,the opening-and-closing valve 7, and the controller 30. The heat sourceside heat exchanger 15 includes the first heat source side heatexchanger 3 and the second heat source side heat exchanger 4 connectedin parallel between the flow switching device 5 and the expansion valve22 a. The opening-and-closing valve 7 is provided on downstream of thesecond heat source side heat exchanger 4 through which refrigerant flowsduring the defrosting operation. When the defrosting operation isperformed, the controller 30 controls the flow switching device 5 sothat the refrigerant discharged from the compressor 2 flows into theheat source side heat exchanger 15. The controller 30 includes the firstdefrosting unit 54, the determination unit 52, and the second defrostingunit 55. When the defrosting operation is started, the first defrostingunit 54 switches the opening-and-closing valve 7 from an open state to aclosed state. The determination unit 52 determines a point in time whendefrosting targets to be defrosted are switched. The second defrostingunit switches the opening-and-closing valve 7 from the closed state tothe open state in accordance with the point in time determined by thedetermination unit 52.

In Embodiment 1, the first defrosting unit 54 closes theopening-and-closing valve 7 when defrosting is started, and thus therefrigerant discharged from the compressor 2 flows intensively to thefirst heat source side heat exchanger 3 of two heat source side heatexchangers. Subsequently, the second defrosting unit 55 opens theopening-and-closing valve 7. Thus, the refrigerant flows to the secondheat source side heat exchanger 4 and also flows to the first heatsource side heat exchanger 3. When the refrigerant flows to the two heatsource side heat exchangers, most of the heat of the refrigerant isconsumed in the second heat source side heat exchanger 4, and also frostremaining in the first heat source side heat exchanger 3 melts. Thus,the heat of the refrigerant is kept from being uselessly consumed incomparison with a case where two heat source side heat exchangersconnected in series are simultaneously defrosted. Consequently, the twoheat source side heat exchangers can be efficiently defrosted.

(Modification 1)

Modification 1 is the case where the refrigerant temperature sensor 12is not provided in the refrigeration cycle apparatus 1 illustrated inFIG. 1. In Modification 1, components that are the same as componentsdescribed with reference to FIGS. 1 to 5 are denoted by the samereference signs, and a detailed description thereof is omitted.

A configuration of a refrigeration cycle apparatus in Modification 1will be described. FIG. 6 is a refrigerant circuit diagram illustratingan example configuration of the refrigeration cycle apparatus inModification 1. FIG. 7 is a functional block diagram illustrating anexample configuration of the controller in Modification 1.

In a heat source side unit 10 a in a refrigeration cycle apparatus 1 a,the refrigerant temperature sensor 12 illustrated in FIG. 1 is notprovided. After the determination unit 52 transmits the switchinginstruction information to the second defrosting unit 55, thedetermination unit 52 determines whether or not the time t1 measured bythe timer 53 is not less than a predetermined time threshold tth2. Therelationship between the time thresholds tth1 and tth2 is tth1<tth2.When the time t1 reaches not less than the time threshold tth2, thedetermination unit 52 transmits the defrosting completion information tothe refrigeration cycle control unit 51.

The operation of the refrigeration cycle apparatus 1 a in Modification 1will be described with reference to FIG. 5. Here, an operation differentfrom the operations illustrated in FIG. 5 will be described, and adetailed description of operations similar to the operations describedwith reference to FIG. 5 is omitted.

In step S106, the determination unit 52 determines whether or not thetime t1 measured by the timer 53 has reached not less than the timethreshold tth2. As a result of a determination made in step S106, whenthe time t1 reaches not less than the time threshold tth2, thedetermination unit 52 transmits the defrosting completion information tothe refrigeration cycle control unit 51.

In Modification 1, even when the refrigerant temperature sensor 12 isnot provided, effects of Embodiment 1 can be obtained.

(Modification 2)

Modification 2 is the case where a flow control valve and a refrigeranttemperature sensor are provided in the first liquid pipe 44 a in therefrigeration cycle apparatus 1 illustrated in FIG. 1. In Modification2, components that are the same as components described with referenceto FIGS. 1 to 7 are denoted by the same reference signs, and a detaileddescription thereof is omitted.

A configuration of a refrigeration cycle apparatus in Modification 2will be described. FIG. 8 is a refrigerant circuit diagram illustratingan example configuration of the refrigeration cycle apparatus inModification 2. FIG. 9 is a functional block diagram illustrating anexample configuration of the controller in Modification 2. Asillustrated in FIG. 8, in the first liquid pipe 44 a in a heat sourceside unit 10 b in a refrigeration cycle apparatus 1 b, a refrigeranttemperature sensor 12 a and a flow control valve 9 are provided. Therefrigerant temperature sensor 12 a detects a temperature Tn1 ofrefrigerant that flows through the first liquid pipe 44 a. The flowcontrol valve 9 can be switched, of a closed state and an open state,from one state to the other state.

Furthermore, the flow control valve 9 can adjust a flow rate ofrefrigerant that circulates by changing its opening degree. Asillustrated in FIG. 9, the controller 30 in Modification 2 does notinclude the timer 53 illustrated in FIG. 2. Regarding the temperatureTn1 of refrigerant, the controller 30 stores, in advance, thetemperature threshold Ta as a criterion value for determining a point intime when defrosting targets to be defrosted are switched. Values of Taand Tb may be the same or may be different.

Next, the operation of the refrigeration cycle apparatus 1 b inModification 2 will be described. FIG. 10 is a flowchart illustrating anexample of an operation procedure performed by the refrigeration cycleapparatus illustrated in FIG. 8. Assume that the refrigeration cycleapparatus 1 b is performing the heating operation before starting theoperation procedure illustrated in FIG. 10 and the flow control valve 9and the opening-and-closing valve 7 are in an open state. Operations ofsteps S201 and S202 illustrated in FIG. 10 are similar to the operationsof steps S101 and S102 described with reference to FIG. 5, and thus adetailed description thereof is omitted.

After a determination is made in step S201, when the determination unit52 receives defrosting start information from the refrigeration cyclecontrol unit 51, the determination unit 52 transfers the defrostingstart information to the first defrosting unit 54 and also monitors thetemperature Tn1 of refrigerant detected by the refrigerant temperaturesensor 12 a. When the first defrosting unit 54 receives the defrostingstart information from the determination unit 52, the first defrostingunit 54 closes the opening-and-closing valve 7 (step S203). Thedetermination unit 52 determines whether or not the temperature Tn1 ofrefrigerant has reached not less than the temperature threshold Ta (stepS204). When the temperature Tn1 of refrigerant reaches not less than thetemperature threshold Ta in step S204, the determination unit 52transmits switching instruction information to the second defrostingunit 55.

When the second defrosting unit 55 receives the switching instructioninformation from the determination unit 52, the second defrosting unit55 opens the opening-and-closing valve 7 (step S205) and closes the flowcontrol valve 9 (step S206). After the determination unit 52 transmitsthe switching instruction information to the second defrosting unit 55,the determination unit 52 determines whether or not the temperature Tn2of refrigerant detected by a refrigerant temperature sensor 12 b hasreached not less than the temperature threshold Tb (step S207). When thetemperature Tn2 of refrigerant reaches not less than the temperaturethreshold Tb, the determination unit 52 determines that defrosting ofthe heat source side heat exchanger 15 has been completed and transmitsdefrosting completion information to the second defrosting unit 55 andthe refrigeration cycle control unit 51.

When the second defrosting unit 55 receives the defrosting completioninformation from the determination unit 52, the second defrosting unit55 opens the flow control valve 9 (step S208). When the refrigerationcycle control unit 51 receives the defrosting completion informationfrom the determination unit 52, the refrigeration cycle control unit 51controls the flow switching device 5 to switch between the flow passages(step S209). Thus, the refrigerant discharged from the compressor 2flows through the flow switching device 5 and flows into the load sideunits 20 a and 20 b. The operation mode of the refrigeration cycleapparatus 1 returns from the defrosting operation to the heatingoperation.

Incidentally, in step S206 illustrated in FIG. 10, although the seconddefrosting unit 55 closes the flow control valve 9, the seconddefrosting unit 55 does not completely close the flow control valve 9and may reduce the opening degree of the flow control valve 9 to cause alittle refrigerant to circulate. In this case, in step S208, the seconddefrosting unit 55 opens the flow control valve 9 fully.

In Modification 2, valves that shut off flows of refrigerant areprovided in the respective liquid pipes of the first heat source sideheat exchanger 3 and the second heat source side heat exchanger 4 thatare connected in parallel. In the defrosting operation, therefrigeration cycle apparatus 1 b in Modification 2 performs opening andclosing control of each valve to first intensively defrost the firstheat source side heat exchanger 3 and then to intensively defrost theother second heat source side heat exchanger 4, and thus defrosting canbe performed reliably and efficiently.

Furthermore, the determination unit 52 determines, by using thetemperature Tn1 of refrigerant, a point in time when an object to bemainly defrosted is switched from the first heat source side heatexchanger 3 to the second heat source side heat exchanger 4. For thisreason, the determination unit 52 can determine whether or not frost hasremained in the first heat source side heat exchanger 3 more accuratelythan by using the time t1 measured by the timer 53. Furthermore, inModification 2, the timer 53 does not have to be provided in thecontroller 30.

(Modification 3)

Modification 3 is the case where three or more heat source side heatexchangers are connected in parallel in the refrigeration cycleapparatus 1 illustrated in FIG. 1. In Modification 3, components thatare the same as components described with reference to FIGS. 1 to 10 aredenoted by the same reference signs, and a detailed description thereofis omitted.

A configuration of a refrigeration cycle apparatus in Modification 2will be described. FIG. 11 is a refrigerant circuit diagram illustratingan example configuration of the refrigeration cycle apparatus inModification 3. As illustrated in FIG. 11, in a heat source side unit 10c in a refrigeration cycle apparatus 1 c, a third heat source side heatexchanger 8 connected in parallel with the first heat source side heatexchanger 3 and the second heat source side heat exchanger 4 isprovided. The third heat source side heat exchanger 8 is connected tothe gas pipe 41 via a third gas pipe 43 c and is connected to the liquidpipe 47 via a third liquid pipe 44 c.

In the third liquid pipe 44 c, a refrigerant temperature sensor 12 c anda second flow control valve 9 b are provided. The refrigeranttemperature sensor 12 c detects a temperature Tn3 of refrigerant thatflows through the third liquid pipe 44 c. The determination unit 52compares the temperature Tn3 of refrigerant with a predeterminedtemperature threshold Td and switches between defrosting targets to bedefrosted when the temperature Tn3 of refrigerant reaches not less thanthe temperature threshold Td. Incidentally, configurations of a firstflow control valve 9 a and the second flow control valve 9 b are similarto the configuration of the flow control valve 9, a configuration of therefrigerant temperature sensor 12 c is similar to the configuration ofthe refrigerant temperature sensor 12, and thus a detailed descriptionof these is omitted.

The operation of the refrigeration cycle apparatus 1 c in Modification 2will be described with reference to FIG. 10. Here, an operationdifferent from the operations illustrated in FIG. 10 will be described,and a detailed description of operations similar to the operationsdescribed with reference to FIG. 10 is omitted. As a default state, theopening-and-closing valve 7, the first flow control valve 9 a, and thesecond flow control valve 9 b are in an open state.

In step S203, when the first defrosting unit 54 receives the defrostingstart information from the determination unit 52, the first defrostingunit 54 maintains the first flow control valve 9 a in the open state andcloses the opening-and-closing valve 7 and the second flow control valve9 b. In step S206, the second defrosting unit 55 closes the first flowcontrol valve 9 a. In step S207, when the temperature Tn2 of refrigerantreaches not less than the temperature threshold Tb, the determinationunit 52 transmits switching instruction information to the seconddefrosting unit 55. When the second defrosting unit 55 receives theswitching instruction information from the determination unit 52 afterstep S206, the second defrosting unit 55 closes the opening-and-closingvalve 7 and opens the second flow control valve 9 b.

After the determination unit 52 transmits the switching instructioninformation to the second defrosting unit 55 in accordance with a resultof a determination made in step S207, the determination unit 52determines whether or not the temperature Tn3 of refrigerant detected bythe refrigerant temperature sensor 12 c has reached not less than thetemperature threshold Td. When the temperature Tn3 of refrigerantreaches not less than the temperature threshold Td, the determinationunit 52 determines that defrosting of the heat source side heatexchanger 15 has been completed and transmits defrosting completioninformation to the second defrosting unit 55 and the refrigeration cyclecontrol unit 51. Subsequently, the controller 30 performs the operationsof steps S208 and S209.

Although FIG. 11 illustrates the case where three heat source side heatexchangers are connected in parallel, the number of heat source sideheat exchangers connected in parallel may be four or more. In this case,a flow control device and a refrigerant temperature sensor are providedon a liquid pipe of each heat source side heat exchanger. Furthermore,in the refrigeration cycle apparatus 1 c illustrated in FIG. 11, thedetermination unit 52 may determine, in accordance with the time t1measured by the timer 53 illustrated in FIG. 2, a point in time whendefrosting targets to be defrosted are switched. In this case, therefrigerant temperature sensors 12 a to 12 c do not have to be provided.

In Modification 3, even when the number of heat source side heatexchangers connected in parallel is three or more, defrosting can beefficiently performed.

Embodiment 2

A refrigeration cycle apparatus in Embodiment 2 is a refrigeration cycleapparatus in which a header is provided for a heat source side heatexchanger, and the header splits refrigerant that circulates intostreams and merges streams of the refrigerant. In Embodiment 2,components that are the same as components described in Embodiment 1 aredenoted by the same reference signs, and a detailed description thereofis omitted.

A configuration of the refrigeration cycle apparatus in Embodiment 2will be described. FIG. 12 is a refrigerant circuit diagram illustratingan example configuration of the refrigeration cycle apparatus accordingto Embodiment 2. A refrigeration cycle apparatus 1 d includes a heatsource side unit 10 d. In the heat source side unit 10 d, a first gasheader 61 is provided on a first gas pipe 43 a side of the first heatsource side heat exchanger 3, and a first liquid header 62 is providedon a first liquid pipe 44 a side of the first heat source side heatexchanger 3. Furthermore, in the heat source side unit 10 d, a secondgas header 63 is provided on a second gas pipe 43 b side of the secondheat source side heat exchanger 4, and a second liquid header 64 isprovided on a second liquid pipe 44 b side of the second heat sourceside heat exchanger 4.

FIG. 13 is a side view illustrating an example configuration of thefirst heat source side heat exchanger illustrated in FIG. 12. FIG. 14 isa side view illustrating an example configuration of the second heatsource side heat exchanger illustrated in FIG. 12. For convenience ofexplanation, FIGS. 13 and 14 illustrate the X axis and the Z axis todefine directions. A direction opposite to a Z-axis arrow illustrated inFIGS. 13 and 14 is a gravity direction. Solid line arrows illustrated inFIGS. 13 and 14 represent directions in which refrigerant flows when therefrigeration cycle apparatus 1 performs the cooling operation and thedefrosting operation. Dashed line arrows illustrated in FIGS. 13 and 14represent directions in which refrigerant flows when the refrigerationcycle apparatus 1 performs the heating operation.

As illustrated in FIG. 13, the first heat source side heat exchanger 3includes a plurality of heat-transfer tubes 45 a and a plurality ofheat-transfer fins 46 a. The first gas pipe 43 a is connected to thefirst gas header 61. A position at which the first gas pipe 43 a isconnected to the first gas header 61 is a middle portion of the heightthat is the length of the first gas header 61 in a direction (Z-axisarrow direction) perpendicular to the ground. The middle portion is notlimited to the exact middle position of the height of the first gasheader 61 and includes a certain range of heights based on the middleposition. The first liquid pipe 44 a is connected to a lower portion ofthe first liquid header 62. When the refrigeration cycle apparatus 1performs the cooling operation and the defrosting operation, the firstgas header 61 splits refrigerant flowing in from the first gas pipe 43 ainto streams flowing through the plurality of heat-transfer tubes 45 a.When the refrigeration cycle apparatus 1 performs the heating operation,the first gas header 61 merges streams of refrigerant flowing in fromthe plurality of heat-transfer tubes 45 a and causes the refrigerant toflow to the first gas pipe 43 a.

As illustrated in FIG. 14, the second heat source side heat exchanger 4includes a plurality of heat-transfer tubes 45 b and a plurality ofheat-transfer fins 46 b. The second gas pipe 43 b is connected to thesecond gas header 63. A position at which the second gas pipe 43 b isconnected to the second gas header 63 is a middle portion of the heightthat is the length of the second gas header 63 in a direction (Z-axisarrow direction) perpendicular to the ground. The middle portion is notlimited to the exact middle position of the height of the second gasheader 63 and includes a certain range of heights based on the middleposition. The second liquid pipe 44 b is connected to a lower portion ofthe second liquid header 64. When the refrigeration cycle apparatus 1performs the cooling operation and the defrosting operation, the secondgas header 63 splits refrigerant flowing in from the second gas pipe 43b into streams flowing through the plurality of heat-transfer tubes 45b. When the refrigeration cycle apparatus 1 performs the heatingoperation, the second gas header 63 merges streams of refrigerantflowing in from the plurality of heat-transfer tubes 45 b and causes therefrigerant to flow to the second gas pipe 43 b.

In Embodiment 2, the height of the first heat source side heat exchanger3 is equal to the height of the second heat source side heat exchanger4, and the number of the heat-transfer tubes 45 a is equal to the numberof the heat-transfer tubes 45 b. Although FIGS. 13 and 14 illustrate thecase where the number of the heat-transfer tubes 45 a and the number ofthe heat-transfer tubes 45 b are 13, the numbers of the heat-transfertubes 45 a and the heat-transfer tubes 45 b are not limited to 13.

The operation of the refrigeration cycle apparatus 1 d in Embodiment 2is similar to the operation procedure described with reference to FIG.5, and thus a detailed description thereof is omitted.

To explain functions and effects achieved by the refrigeration cycleapparatus 1 d in Embodiment 2 in an easy-to-understand fashion, aconfiguration of a refrigeration cycle apparatus in a comparativeexample will be described. FIG. 15 is a refrigerant circuit diagramillustrating an example configuration of the refrigeration cycleapparatus in the comparative example. Components that are the same ascomponents described with reference to FIGS. 1 and 12 are denoted by thesame reference signs, and a detailed description thereof is omitted.

As illustrated in FIG. 15, a refrigeration cycle apparatus 100 in thecomparative example includes a heat source side unit 110, the load sideunits 20 a and 20 b, and a controller 130. On the basis of a directionin which refrigerant flows during the defrosting operation, arefrigerant temperature sensor 121 is provided in the liquid pipe 47downstream from a position at which the first liquid pipe 44 a and thesecond liquid pipe 44 b are joined. The refrigerant temperature sensor121 detects a temperature Tr of refrigerant that flows through theliquid pipe 47 and transmits information on the temperature Tr ofrefrigerant to the controller 130. A hardware configuration of thecontroller 130 is similar to the configuration described with referenceto FIGS. 3 and 4, and thus a detailed description thereof is omitted.

In comparison with the configuration illustrated in FIG. 12, theopening-and-closing valve 7 illustrated in FIG. 1 is not provided in thesecond liquid pipe 44 b in the heat source side unit 110 illustrated inFIG. 15. When the refrigeration cycle apparatus 100 performs thedefrosting operation, the controller 130 compares the temperature Tr ofrefrigerant with a predetermined temperature threshold Tc. Subsequently,when the temperature Tr of refrigerant reaches not less than thetemperature threshold Tc, the controller 130 determines that defrostinghas been completed. The temperature threshold Tc is, for example, 10degrees C. The relationship between the temperature thresholds Tb and Tcis Tc>Tb. Furthermore, when the temperature threshold Tc is comparedwith the temperature threshold Ta described in Modification 2, therelationship of Ta<Tc is established.

Next, the operation of the refrigeration cycle apparatus 100 in thecomparative example illustrated in FIG. 15 will be described withreference to FIG. 16. FIG. 16 is a flowchart illustrating an example ofan operation procedure performed by the refrigeration cycle apparatus inthe comparative example illustrated in FIG. 15. Assume that therefrigeration cycle apparatus 100 is performing the heating operationbefore starting the operation procedure illustrated in FIG. 16.

The controller 130 determines whether or not the temperature Te ofrefrigerant has reached not more than the temperature threshold T0 (stepS1001). When the temperature Te of refrigerant reaches not more than thetemperature threshold T0 in step S1001, the controller 130 determinesthat frost has adhered to the heat source side heat exchanger 15 andcontrols the flow switching device 5 to switch between the flow passages(step S1002). Thus, the refrigerant discharged from the compressor 2flows through the flow switching device 5 and flows into the heat sourceside heat exchanger 15.

Subsequently, the controller 130 determines whether or not thetemperature Tr of refrigerant is not less than the temperature thresholdTc (step S1003). When the temperature Tr of refrigerant reaches not lessthan the temperature threshold Tc in step S1003, the controller 130determines that defrosting of the heat source side heat exchanger 15 hasbeen completed and controls the flow switching device 5 to switchbetween the flow passages (step S1004). The operation mode of therefrigeration cycle apparatus 100 returns from the defrosting operationto the heating operation.

While the refrigeration cycle apparatus 100 is performing the defrostingoperation, in the first heat source side heat exchanger 3 illustrated inFIG. 13, gaseous refrigerant flows into the middle portion of the firstgas header 61 from the first gas pipe 43 a. The gaseous refrigeranthaving flowed into the first gas header 61 is split into streams flowingthrough the plurality of heat-transfer tubes 45 a, and the refrigerantis likely to accumulate in a lower heat-transfer tube 45 a in the firstheat source side heat exchanger 3 due to pressure loss. As in the firstheat source side heat exchanger 3, in the second heat source side heatexchanger 4 illustrated in FIG. 14, refrigerant is likely to accumulatein a lower heat-transfer tube 45 b in the second heat source side heatexchanger 4 in the defrosting operation.

FIG. 17 includes graphs illustrating an example of the relationshipbetween a refrigerant flow rate and a position of a heat source sideheat exchanger during the defrosting operation. In FIG. 17, thehorizontal axis represents refrigerant flow rate, and the vertical axisrepresents height Hu of a heat-transfer tube 45 a in a verticaldirection (Z-axis arrow direction) of the first heat source side heatexchanger 3 illustrated in FIG. 13. In the vertical axis in FIG. 17,among the plurality of heat-transfer tubes 45 a in the first heat sourceside heat exchanger 3, the height of a lowermost heat-transfer tube 45 ais denoted by Hu1, the height of an uppermost heat-transfer tube 45 a isdenoted by Hun. In FIG. 17, a solid line graph represents the case ofthe refrigeration cycle apparatus 1 d in Embodiment 2, and a dashed linegraph represents the case of the refrigeration cycle apparatus 100 inthe comparative example illustrated in FIG. 15. Furthermore, the secondheat source side heat exchanger 4 also has a tendency similar to that ofthe graphs illustrated in FIG. 17, and thus a description of the case ofthe second heat source side heat exchanger 4 is omitted here.

In the defrosting operation performed by the refrigeration cycleapparatus 100 in the comparative example, when refrigerant is split intostreams flowing through the first heat source side heat exchanger andthe second heat source side heat exchanger, a refrigerant flow rate in alower section in the heat source side heat exchanger 15 is smaller thanthat in an upper section as represented by the dashed line graph in FIG.17. This is because, in the case where refrigerant is split into streamsflowing through a plurality of heat-transfer tubes from a middle portionof a header as described with reference to FIGS. 13 and 14, the flow ofrefrigerant deteriorates due to pressure loss and the refrigerant islikely to accumulate in the lower section.

Because of this, in the refrigeration cycle apparatus 100 in thecomparative example, in consideration of a flow rate of refrigerant thatflows to a lower heat-transfer tube in the heat source side heatexchanger 15, it takes a long time for defrosting of the heat sourceside heat exchanger 15 to be completed, and the temperature threshold Tcis set to a high value. As a result, as represented by the dashed linegraph in FIG. 17, the refrigerant uselessly flows in the upper sectionuntil defrosting of the lower heat-transfer tube in the heat source sideheat exchanger 15 is completed.

On the other hand, in the refrigeration cycle apparatus 1 d inEmbodiment 2, as represented by the solid line graph in FIG. 17,refrigerant flow rates are less affected by differences in the heightsof the heat-transfer tubes 45 a in the first heat source side heatexchanger 3 than those in the comparative example, and the plurality ofheat-transfer tubes 45 a allow the refrigerant to uniformly flowtherethrough. Thus, the temperature threshold Tb can be set to atemperature lower than the temperature threshold Tc, and defrosting canbe performed more efficiently than in the comparative example.

The refrigeration cycle apparatus 1 d in Embodiment 2 includes the firstgas header 61 and the second gas header 63. In the defrosting operation,the first gas header 61 splits refrigerant flowing into the first heatsource side heat exchanger 3 into streams flowing through the pluralityof heat-transfer tubes 45 a, and the second gas header 63 splitsrefrigerant flowing into the second heat source side heat exchanger 4into streams flowing through the plurality of heat-transfer tubes 45 b.The first gas pipe 43 a is connected to the middle portion in thegravity direction of the first gas header 61, and the second gas pipe 43b is connected to the middle portion in the gravity direction of thesecond gas header 63.

In Embodiment 2, in the defrosting operation, as described in Embodiment1, when the opening degree of the opening-and-closing valve 7 isadjusted, flow rates of respective refrigerant streams that flow to thefirst heat source side heat exchanger 3 and the second heat source sideheat exchanger 4 are increased. In Embodiment 2, accumulation ofrefrigerant in a lower section in the heat source side heat exchangercaused by differences in the heights of the heat-transfer tubes isinhibited, and a flow rate of refrigerant in the lower sectionincreases. As a result, frost having adhered to the lower section in theheat source side heat exchanger can be removed reliably and efficiently.The temperature thresholds Ta and Tb can be set to a value smaller thanthe temperature threshold Tc in the comparative example, and thus adefrosting time period is reduced in comparison with that in thecomparative example, thereby enabling efficient defrosting.

Embodiment 3

A refrigeration cycle apparatus in Embodiment 3 is a refrigeration cycleapparatus in which the number of heat-transfer tubes in the first heatsource side heat exchanger is different from the number of heat-transfertubes in the second heat source side heat exchanger. In Embodiment 3,components that are the same as components described in Embodiments 1and 2 are denoted by the same reference signs, and a detaileddescription thereof is omitted.

A configuration of the refrigeration cycle apparatus in Embodiment 3will be described. FIG. 18 is a refrigerant circuit diagram illustratingan example configuration of the refrigeration cycle apparatus accordingto Embodiment 3. A refrigeration cycle apparatus 1 e includes a heatsource side unit 10 e. The first heat source side heat exchanger 3provided in the heat source side unit 10 e includes a first divisionheat exchanger 3-1 and a second division heat exchanger 3-2 that areconnected in parallel.

The first gas pipe 43 a is split into gas branch pipes 43 a-1 and 43-2.The gas branch pipe 43 a-1 is connected to the first division heatexchanger 3-1, and the gas branch pipe 43 a-2 is connected to the seconddivision heat exchanger 3-2. The first liquid pipe 44 a is split intoliquid branch pipes 44 a-1 and 44 a-2. The liquid branch pipe 44 a-1 isconnected to the first division heat exchanger 3-1, and the liquidbranch pipe 44 a-2 is connected to the second division heat exchanger3-2.

In the first division heat exchanger 3-1, the first gas header 61 isprovided on a gas branch pipe 43 a-1 side, and the first liquid header62 is provided on a liquid branch pipe 44 a-1 side. In the seconddivision heat exchanger 3-2, a first gas header 65 is provided on a gasbranch pipe 43 a-2 side, and a first liquid header 66 is provided on aliquid branch pipe 44 a-2 side. A configuration of the first gas header65 is similar to that of the first gas header 61, a configuration of thefirst liquid header 66 is similar to that of the first liquid header 62,and thus a detailed description of these is omitted.

FIG. 19 is an external perspective view illustrating an exampleconfiguration of the heat source side unit illustrated in FIG. 18. FIG.20 is an external perspective view of the heat source side unitillustrated in FIG. 18 as seen from a direction different from that inFIG. 19. The first division heat exchanger 3-1 and the second divisionheat exchanger 3-2 have the same height that is the length in adirection (Z-axis arrow direction) perpendicular to the ground, and theheight is denoted by L1. When the height of the second heat source sideheat exchanger 4 is denoted by L2, the relationship between the heightsL1 and L2 is L2<L1. In example configurations illustrated in FIGS. 19and 20, for example, the relationship of L2=L1×(⅔) is established.

FIG. 21 is a schematic view illustrating the layout of the heat sourceside heat exchangers in the heat source side unit illustrated in FIG. 20as seen from above. The first division heat exchanger 3-1 and the seconddivision heat exchanger 3-2 as seen from above are L-shaped asillustrated in FIG. 21. The second heat source side heat exchanger 4 asseen from above is linear-shaped as illustrated in FIG. 21. In anexample configuration illustrated in FIG. 21, although the firstdivision heat exchanger 3-1 is L-shaped, if the first division heatexchanger 3-1 is straightened into a linear shape, the linear length ofthe first division heat exchanger 3-1 is equal to the linear length ofthe second heat source side heat exchanger 4.

FIG. 22 is a side view illustrating an example configuration of thefirst division heat exchanger illustrated in FIG. 19. The seconddivision heat exchanger 3-2 has the same configuration as the firstdivision heat exchanger 3-1, and thus the second division heat exchanger3-2 is not illustrated in FIG. 22. Furthermore, FIG. 22 illustrates thefirst division heat exchanger 3-1 obtained by straightening the L-shapedfirst division heat exchanger 3-1 illustrated in FIG. 21 into a linearshape. FIG. 23 is a side view illustrating an example configuration ofthe second heat source side heat exchanger illustrated in FIG. 20. Forconvenience of explanation, FIGS. 22 and 23 illustrate the X axis andthe Z axis to define directions. However, an X-axis arrow does not haveto correspond to X-axis arrows illustrated in FIGS. 19 and 20.

The number of heat-transfer tubes 45 a in the first division heatexchanger 3-1 illustrated in FIG. 22 is 13. The number of heat-transfertubes 45 b in the second heat source side heat exchanger 4 illustratedin FIG. 23 is 9. The number of heat-transfer tubes 45 a in the firstdivision heat exchanger 3-1 is larger than the number of heat-transfertubes 45 b in the second heat source side heat exchanger 4. A ratio ofthe number of heat-transfer tubes 45 a in the first division heatexchanger 3-1 to the number of heat-transfer tubes 45 b in the secondheat source side heat exchanger 4 is a value close to a ratio of theheight L1 of the first heat source side heat exchanger 3 to the heightL2 of the second heat source side heat exchanger 4 (L1:L2)=3:2.

In Embodiment 3, assuming that the length of the heat-transfer tubes 45a illustrated in FIG. 22 is equal to the length of the heat-transfertubes 45 b illustrated in FIG. 23, the number of heat-transfer tubes tobe defrosted in the first heat source side heat exchanger 3 is comparedwith that in the second heat source side heat exchanger 4. From theratio of L1/L2, the number of heat-transfer tubes 45 a in the firstdivision heat exchanger 3-1 is (3/2) times the number of heat-transfertubes 45 b in the second heat source side heat exchanger 4. The numberof heat-transfer tubes 45 a in the first division heat exchanger 3-1 isequal to the number of heat-transfer tubes 45 a in the second divisionheat exchanger 3-2, and thus the number of heat-transfer tubes 45 a inthe first heat source side heat exchanger 3 is three times the number ofheat-transfer tubes 45 b in the second heat source side heat exchanger4. Incidentally, the numbers of heat-transfer tubes 45 a in the firstdivision heat exchanger 3-1 and the second division heat exchanger 3-2,and the number of heat-transfer tubes 45 b in the second heat sourceside heat exchanger 4 are not limited to the numbers illustrated inFIGS. 22 and 23.

The operation of the refrigeration cycle apparatus 1 e in Embodiment 3is similar to the operation procedure described with reference to FIG.5, and thus a detailed description thereof is omitted.

Referring to FIG. 5, the opening-and-closing valve 7 is closed from thestart of the defrosting operation based on the operation of step S102until the time when the time t1 reaches the time threshold tth1, andthus the first heat source side heat exchanger 3 is intensivelydefrosted. Subsequently, the opening-and-closing valve 7 is opened, anddefrosting of the second heat source side heat exchanger 4 is started,while the refrigerant also flows to the first heat source side heatexchanger 3. The amount of refrigerant that flows to the first heatsource side heat exchanger 3 is greater than the amount of refrigerantthat flows to the second heat source side heat exchanger 4. For thisreason, even if the number of heat-transfer tubes 45 a in the first heatsource side heat exchanger 3 is larger than the number of heat-transfertubes 45 b in the second heat source side heat exchanger 4, therefrigeration cycle apparatus 1 e can time the completion of defrostingof the first heat source side heat exchanger 3 to coincide with a pointin time when defrosting of the second heat source side heat exchanger 4is completed.

In the refrigeration cycle apparatus 1 e in Embodiment 3, the number ofheat-transfer tubes 45 a in the first heat source side heat exchanger 3is larger than the number of heat-transfer tubes in the second heatsource side heat exchanger 4. In Embodiment 3, the amount of refrigerantthat flows to the first heat source side heat exchanger 3 is greaterthan the amount of refrigerant that flows to the second heat source sideheat exchanger 4, and thus the completion of defrosting of the firstheat source side heat exchanger 3 can be timed to coincide with a pointin time when defrosting of the second heat source side heat exchanger 4is completed.

(Modification 4)

A refrigeration cycle apparatus in Modification 4 is a refrigerationcycle apparatus in which, in the refrigerant circuits 60 a and 60 billustrated in FIG. 18, the flow control valve 9 is provided in thefirst liquid pipe 44 a. In Modification 4, components that are the sameas components described with reference to FIGS. 18 to 23 are denoted bythe same reference signs, and a detailed description thereof is omitted.

A configuration of the refrigeration cycle apparatus in Modification 4will be described. FIG. 24 is a refrigerant circuit diagram illustratingan example configuration of the refrigeration cycle apparatus inModification 4. In a heat source side unit 10 f in a refrigeration cycleapparatus 1 f, the flow control valve 9 is provided in the first liquidpipe 44 a.

Incidentally, the operation of the refrigeration cycle apparatus 1 f issimilar to the procedure illustrated in FIG. 10 except that a point intime when defrosting targets to be defrosted are switched is determinedin accordance with the time t1 measured by the timer 53 in step S207illustrated in FIG. 10, and thus a detailed description thereof isomitted. The refrigerant temperature sensor 12 may be provided in theliquid pipe 47 near the confluence of the first liquid pipe 44 a and thesecond liquid pipe 44 b in place of the second liquid pipe 44 b.

In Modification 4, valves that shut off flows of refrigerant areprovided in the respective liquid pipes of the first heat source sideheat exchanger 3 and the second heat source side heat exchanger 4. Inthe defrosting operation, the refrigeration cycle apparatus 1 f inModification 4 performs opening and closing control of each valve tofirst defrost the first heat source side heat exchanger 3 and then todefrost the other second heat source side heat exchanger 4, and thusdefrosting can be performed reliably and efficiently.

Although, in Embodiment 3, the description based on the refrigerationcycle apparatus 1 d described in Embodiment 2 has been given, Embodiment3 may be applied to the refrigeration cycle apparatus 1 described inEmbodiment 1. Furthermore, in each of Embodiments 2 and 3, amongModifications 1 to 3, any Modifications may be combined.

1. A refrigeration cycle apparatus comprising: a compressor configuredto compress and discharge refrigerant; an expansion valve configured toreduce pressure of the refrigerant to cause the refrigerant to expand; aload side heat exchanger connected to the expansion valve; a four-wayvalve connected to the compressor and the load side heat exchanger; aheat source side heat exchanger including a first heat source side heatexchanger and a second heat source side heat exchanger connected inparallel between the four-way valve and the expansion valve; a gas pipeconfigured to join a first gas pipe connected to the first heat sourceside heat exchanger and a second gas pipe connected to the second heatsource side heat exchanger to allow the first gas pipe and the secondgas pipe to communicate with the flow switching device; a first gasheader configured to split the refrigerant flowing into the first heatsource side heat exchanger including a plurality of first heat-transfertubes from the compressor via the four-way valve into streams flowingthrough the plurality of first heat-transfer tubes; a second gas headerconfigured to split the refrigerant flowing into the second heat sourceside heat exchanger including a plurality of second heat-transfer tubesfrom the compressor via the four-way valve into streams flowing throughthe plurality of second heat-transfer tubes; an opening-and-closingvalve provided on downstream of the second heat source side heatexchanger through which the refrigerant flows during a defrostingoperation; and a controller configured to, when the defrosting operationis performed, control the four-way valve so that the refrigerantdischarged from the compressor flows into the heat source side heatexchanger, wherein a number of the plurality of first heat-transfertubes is larger than a number of the plurality of second heat-transfertubes, the first gas pipe is connected to a middle portion in a gravitydirection of the first gas header, the second gas pipe is connected to amiddle portion in the gravity direction of the second gas header, andthe controller is configured to switch the opening-and-closing valvefrom an open state to a closed state when the defrosting operation isstarted, determine a point in time when defrosting targets to bedefrosted are switched, and switch the opening-and-closing valve fromthe closed state to the open state in accordance with the point in timedetermined. 2-3. (canceled)
 4. The refrigeration cycle apparatus ofclaim 1, further comprising a temperature sensor provided on thedownstream of the second heat source side heat exchanger and configuredto detect a temperature of the refrigerant, wherein the controller isconfigured to determine, as the point in time, a time when a valuedetected by the temperature sensor reaches not less than a predeterminedtemperature threshold.
 5. The refrigeration cycle apparatus of claim 1,further comprising a flow control valve provided on downstream of thefirst heat source side heat exchanger through which the refrigerantflows during the defrosting operation, wherein, when the defrostingoperation is started, the controller is configured to maintain the flowcontrol valve in an open state and switch the opening-and-closing valvefrom an open state to a closed state, and wherein, in accordance withthe point in time determined, the controller is configured to switch theflow control valve from the open state to a closed state and switch theopening-and-closing valve from the closed state to the open state. 6.The refrigeration cycle apparatus of claim 5, further comprising atemperature sensor provided on the downstream of the first heat sourceside heat exchanger and configured to detect a temperature of therefrigerant, wherein the controller is configured to determine, as thepoint in time, a time when a value detected by the temperature sensorreaches not less than a predetermined temperature threshold.
 7. Therefrigeration cycle apparatus of claim 1, wherein the controller furtherincludes a timer configured to measure a time period, and wherein thecontroller is configured to determine, as the point in time, a time whena time period measured from start of the defrosting operation by thetimer reaches not less than a predetermined time threshold.
 8. Therefrigeration cycle apparatus of claim 1, further comprising: a thirdheat source side heat exchanger connected in parallel with the firstheat source side heat exchanger and the second heat source side heatexchanger between the four-way valve and the expansion valve; a firstflow control valve provided on downstream of the first heat source sideheat exchanger through which the refrigerant flows during the defrostingoperation; and a second flow control valve provided on downstream of thethird heat source side heat exchanger through which the refrigerantflows during the defrosting operation, wherein, when the defrostingoperation is started, the controller is configured to maintain the firstflow control valve in an open state and switch the opening-and-closingvalve and the second flow control valve from an open state to a closedstate, wherein, in accordance with the point in time determined, thecontroller is configured to switch the first flow control valve from theopen state to a closed state and switch the opening-and-closing valvefrom the closed state to the open state, and wherein, after switchingthe opening-and-closing valve from the closed state to the open state,in accordance with the point in time determined, the controller isconfigured to switch the opening-and-closing valve from the open stateto the closed state and switch the second flow control valve from theclosed state to the open state.